<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <div id="app">app</div>
  </body>
  <script
    src="https://unpkg.com/react@16/umd/react.production.min.js"
    crossorigin
  ></script>
  <script
    src="https://unpkg.com/react-dom@16/umd/react-dom.production.min.js"
    crossorigin
  ></script>
  <script src="https://unpkg.com/babel-standalone@6/babel.min.js"></script>
  <script type="text/babel">
    class App extends React.Component {
      constructor() {
        super()
        this.state = {
          isIS: false,
        }
      }
      loginClick = () => {
        this.setState({
          isIS: !this.state.isIS
        })
      }
      render(h) {
        const {isIs} = this.state
        let btnText = ''
        if(isIs) {
          btnText = '登录'
        } else {
          btnText = '退出'
        }
        return (
          <div class='box'>
            <h2 onClick={() => this.loginClick()}>{btnText}</h2>
            <h2>{this.state.isIS && '456'}</h2>
          </div>
        );
      }
    }

    ReactDOM.render(
      <App />,
      document.getElementById('app')
    )
  </script>
</html>
